Ignition apparatus



May 2, 1950 T. ToGNoLA E-r AL 2,506,560

IGNITION APPARATUS Filed Nov. 8, 1945 ATTORNEY.

Patented May 2, 1950 IGNITION APPARATUS Tullio Tognola, Sidney, and Whitfield C. Smith, Gneonta, N. Y., assignors to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application November s, 1945, serial No. 627,474

6 Claims. 1

This invention relates to ignition apparatus for internal combustion engines and more particularly to a unit which will be called a spark plug although its functions and structure are more complex than the primitive piece of electrical equipment which ordinarily goes by that name.

An object of the present invention is to mount a transformer coil in proximity to an engine. Another object of the invention is to assemble the high tensionportions of an electrical ignition system Within a small compass in proximity to the spark electrodes served thereby. Another object of the invention is to assemble as one unit an ignition coil, a condenser, an air gap, and the electrodes of a spark plug in order to simplify the wiring and ignition system of internal combustion engines operated from remote positions. A particular object of the invention is to employ a condenser and air gap in immediate association with the electrodes of a spark plug. Another object of the invention is to construct the sparking electrodes and the high tension current generating portions of an ignition system as complementary units that can be assembled easily and when so assembled constitute acomplete, radio-shielded plug of unobjectionable size capable of being mounted upon an engine.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not 'intended as a denition of the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a vertical sectional view through a4 spark plug constructed in accordance with thev preferred principles ofthe invention; and

Fig. 2 is a circuiti-diagram illustrative of the a shoulder I4 adapted to make sealing contact` 2 annular flange I5 upon which, in fully assembled relation, a tubular shell I6 is butt soldered. The outer abutting corners of members I5 and I6 may be reduced in order to form a groove I'I for 5 the reception of solder such as silver solder.

with the Wall of an engine cylinder and has an 55 Welding can alternatively be employed for joining the portions I5 and I6 of the shell. An inner electrode I8 encircled by insulation I9 is mounted in the base member I I by means of conical Wedge 2li which conforms to the conical seat I2, and, being of relatively soft material such as copper, is capable of giving satisfactorysupport to the combined structure.

' It is desired to mount the spark generating and regulating means in the closest proximity to the electrodes of the plug without mounting objects of objectionable bulk upon an engine. In order to attain this objective, the transformer windings, a condenser, and a gap cell are constructed as a unit to beA mounted about the center electrode. In the drawing, the numeral 30 signies a sleeve made of some satisfactory dielectric material such as a ceramic, the outer surface of which is provided with a helical groove 3| for the reception of the wires 32 of the primary coil of a transformer. The Wire of this coil need not be insulated if the groove is deep enough, but in other cases it may be advisable to employ a wire having plastic insulation. Such wire is illustrated in the accompanying drawing at 32'. The sleeve 30 has a iiange 33 of annular character at its lower end which is adapted to receive the ange 34 of Ya grounding ring 35 which isv connected through the conical wedge 20 and the base member II to the metal of the motor. One end of the primary winding is secured and electrically connected to the grounding ring 35, at 36.

The grounding ring 35 projects inwardly beyond the wall of the sleeve 30 and serves as a support for a tube 4I of mica or other dielectric material upon which is wound the secondary windings 42, one end 46 of which is grounded and connected to one end of the primary winding 32 at point 36.

The mica tube 4I is preferably provided with a plurality of layers between which, at one end,v

the downturned ends of spring 43 are caught. This spring is electrically connectedto the out:- put end 45 of the secondary and hasan oifset 44 which serves to make firm contact with the end of the center electrode I3 so that discharges from the secondary willl be conducted to the electrode and cause the ignition spark by leap- Ving the gap between electrodes I8 `and I0.

The structure as so far described may be assembled by winding a sufficient number of turns n of mica to provide a support, winding or other- An air gap cell is electrically located between the condenser and the primary and serves, inter alia, the purpose of regulating the charge delivered 'thereto and of offsetting the effect of different air pressures existing at different heights. In the sleeve 39 is a partition 3l beyond which,

toward its upper end, is a recess 38 which is f adapted to receive theair gap cell, generally indicated by the numeral't.

The air gap cell 50 comprises a glass cylinder i .having metallic end pieces' 52, 53 which are connected thereto by fusing the metal and glass togetheruntil .a permanent joint is made. The fusing of the metal Ibases to the glass occurs under slight pressure when both are heated to red heat. The plate 52 carries the high side electrode 54 which may be made of cut nickel or the like, and which is preferably tipped with tungsten as indicated at 5 5. The low side electrode 55 is similarly constituted and is also provided with a tungsten tip 5 7. The tungsten 4tips need not vbe of great size, their general purpose being to prevent the disintegration .of the electrodes under the'eifect of the'electricaldischarge during operation. The tungsten points may Vbe spot welded or silver soldered onto the end of the electrodes. A teaser electrode 69, being a metallic cylinder fitting the inside of the glasscylinder 5i and having one or more tips 6j `extending into relatively `close lproximity to the electrode 5d, is provided for the purpose .of .effecting .ionization of the gas in the spark gap. This teaser electrode is believed to ionize the main gap; it reduces overshooting 'of the gap voltage. Without the teaserV electrode, the gap may not always be broken down at desired voltage, but '.with the teaser electrode present, the vpassing of the spark across the gap at constant breakdown voltage is assured.

The interior of the gap cell is preferably filled with an inert gas'such Vas nitrogen, argon,"nydroby means of a spring 68 and a contact 69. The contact block 61 may be screw threaded into the stopper 64.

A tubular condenser 10 encircles the sleeve 30 and is preferably provided with a snug fit thereabout. A pasage 7| between the stopper S and the metal base member 52, yand passage 'l2 in the side of the sleeve receive Aa, conductor 73 which electrically connects the condenser I6 with the metal base member 52 and the contact 61. The

' other side of the condenser is connected by a gen, or helium at la pressure of about one atmosl phere. Higher pressuresmay be employed and require a higher voltage'to bridge the gap. Lower pressures may be employed with `a corresponding reduction in voltage requirements. By so constructingvthe gapcell the effectof varying atmosphericpressure at different elevations abovethe surface of the earth is avoided.

A passage 5,2 `is provided, between the'upper end of the groove 3| and the recess 38, through which thek primary of the transformer Amay be electrically connected with the metal plate 531thus providing for the transmission of the electric charge which 4passes across thegap to the primary of the transformer. A mounting block 63 isseated ina recess in the partition 3.? vand serves to .support the cell 56. When the cell is emplaced it is xed in position by .means of f a dielectric .stopper 55 that is preferably cemented inthe end of the recess '58. Thisstopperhas a central passageway 65 to receive Va .met'al Contact Vmember V.6 1 electrically .Connected t9 lil-,etal .base member il nonductor. 'i4 to the grounding ring 35.

rlhe structure Aso .assembled constitutes the 4second unit of '.thefspark plug. This second unit .may be telescopedover the insulator I9 until the offset 413 of the spring 43 comes in contact with the upper end Qf the electrode I8 and the ring '35makes contact with Wedge 20, to which it may be Vsoldered or spot welded if desired. Over the assembled structure the shell member I6 is placed, abutting the annular flange vlli ofthe base -member Il andthe two Vare'hutt soldered'to forni a protective, radio-shielding shell. The entirelunt may nowbe, and lI Jreferably is, lled with a plastic.

dielectric substance such 'as polymerized .Cashew nut shell oil whicniills .the spaces .within the shell. This material is indicated generally by, the numeral 8 0 in one portion of the unit, 'but it is to Vbe understood that'it can 'be ,made vto extend throughoutlall: unfilled spaces therewithin except ,the interiorofthecell 5,0'.

The'primary winding'may be bare ,wire when employed in Vslotsfloutis yprefer ably' insulated, for

instance with .plastic insulation, 44if wound ,upon

a sleeve having a relativelylunslotted surface. The tungsten points Yare spot welded or soldered, for instance jbysilver solder, on tthe ends of the gapV housing. It is 4advisable ,to have .large r.electrode surfaces. atthe gap, b ecauscthe larger the surface'fhe smaller. is ythe tvariation in breakdown voltage, so that with electrodes of large facing ma .there is less ovfershopting.` The teaser may beconsidered tofbe acondenserto ground whose function Jin ionizing .the gap far .outweighs the relatively ynegligilglle losses through its condenser action. ',Ihe teaser gap is preferably-smaller'.and preferably 4has .a much 'lower breakdown 'voltage than themain gap. The 'formation of deposits on the main electrodetends `to lower the break"n l down voltage. The use vof v.tungsten faces fon the electrodes tends to reduce the' "formation ,of

deposits. Allurther'more, the `.wider fthe g'ap ,the less the deposit. Therefore, the A-use of thetea's'e'r permits the-.use of ,a Ywider ,gap .at alsatisfactory j. breakdown voltage. The teaserlitsel'f maybe a split spring ring .whichis frictionallyengaged the glass wall of theeellbyitslownspring action. It may also be anchored theretoby .the'same heat treatment ,which anchors .the `metal'ends ,'offthe cellfto the glass.. A'.`th ickness of .005 A inch is adequate for the teaser.

A wiring diagram for .the .apparatus lis Y shown in Fig. 2, Lthe.diagrammatic representat ions of which are given ,the ,numerals of Afthe Aequivalent partsin Figgll. vlhusjwhen ,acharging current, forinstance Vof 4000 volts'lis'brk'enby thedistributor, the condenserdis'charges through .the

gap ,S5- 5.1 to .the `.primary'32, AindlicingV a `current in secondary 42 vby principles-.well understood.y

This structure hasinanyadvantages. Itassembles within `a small` space upon the engine all the Eelements ,essential to V4the generation of v.a hot, high frequency spark. All the parts of the apparals .are-ln balance se that the tendency 0l illlllaleisdlsarls te rlrllrediwe ,destructire vibrations is lacking. Another advantage of the invention is the making of the sparking plug in telescoping units which are easily dismantled or assembled. Another advantage of the invention is in the construction of the primary and secondary coils of the transformer and in the mounting thereof. A further advantage of the invention is in the automatic making of electrical contacts between the several parts of the apparatus when the parts are assembled. Another advantage of the invention is in the separated axial alignment of the gap cell and the electrode. Yet another advantage of the invention is in the concentric arrangement of the several parts. Still another advantage is in the shell structure.

Although only one embodiment of the invention has herein been illustrated and described, it is to be expressly understood that the same is not limited thereto. Various changes may be made in the design and arrangement of the parts Without departing from the spirit and scope of the invention, as will now be clear to those skilled in the art. For a deiinition of the limits of the invention, reference is had primarily to the appended claims.

What is claimed is:

1. A spark plug comprising a metallic cylinder, a center electrode, a transformer encircling -said center electrode, and a, grounding ring encircling said electrode connected with the primary and the secondary of said transformer and to the said metallic cylinder.

2. A transformer of the spark plug type comprising a mica tube having a plurality of layers, a transformer winding, and a iiat spring contact having bent ends diametrically caught between the said layers and connected to said winding.

3. A spark plug comprising an electrode, an insulating sleeve telescoped over said electrode having a recess, a gap cell in said recess, transformer windings carried by said sleeve, a condenser, and means to electrically connect the parts whereby a charging current may be imposed upon the condenser and discharged across the gap to the transformer and the current induced in the transformer may be conducted to said electrode, said connecting means including a connection from the condenser to one terminal of the gap, a connection from the other terminal of the gap to the primary winding of the transformer and a connection from the secondary winding of the transformer to said electrode.

4. In combination with a high frequency spark plug comprising an insulated center electrode assembly mounted in a metallic shell, a unit including a rigid insulator having a recess in each end thereof and having telescopic relation with said assembly, a transformer having a secondary winding mounted on an insulating sleeve and interposed between said assembly and said insulator in one of said recesses and a primary winding around said insulator, resilient means supported by said sleeve for electrically connecting said secondary winding to the electrode of said assembly, a condenser around said insulator and primary winding, means connecting the low potential terminals of said condenser and said windings to said shell, a sealed spark gap mounted in the other of said recesses, means for connecting opposite terminals of said gap to the high potential lterminals of said condenser and primary winding, and means whereby the condenser connected terminal ci said gap may be connected to a source of electrical energy.

5. In combination with a high frequency spark plug comprising an insulated center electrode mounted in a metallic shell, a transformer unit including a rigid insulator having a recess therein and being in telescopic relation with said insulated electrode, a transformer having a secondary winding mounted on an insulating sleeve and interposed between said electrode and said insulator in said recess and a primary winding around the outside oi said insulator, means for electrically connecting said secondary winding to said electrode, and a metallic ring mounted on the end of said insulator for positioning said sleeve and secondary winding in said recess, said ring having electrical connection with said shell and With the low potential ends of said windings.

6. In combination with a high frequency spark plug comprising an insulated center electrode assembly mounted in a metallic shell, a unit slidably mounted in said shell and including a rigid insulator having telescopic relation with said assembly, a transformer coil having a secondary winding within said insulator around said assembly and a primary winding around said insulator, a condenser around said insulator and primary winding, a metallic ring mounted on said insulator for positioning said secondary Winding therein, said ring having electrical connection ywith said shell `and with the low potential terminals of said windings and said condenser, means connecting the high potential end of said secondary Awinding to the electrode of said assembly, and a spark gap interposed between the high potential terminals of said condenser and primary winding.

TULLIO TOGNOLA. WHITFIELD C. SMITH.

REFERENCES CITED The following references are of record in the lle of this patent:

UNITED STATES PATENTSv Number Name Date 1,389,866 Whisler Oct. 18, 1921 2,378,893 Berkey June 26, 1945 2,392,171 Marsh Jan. 1, 1946 2,394,768 Harkness Feb. 12, 1946 

